Torus shapes for torque converters

ABSTRACT

A torque converter in which the output height of the output openings of the stator is higher than the input height of the input openings, producing a stator with a diffuser effect.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Application No. 60/791,658, filed Apr. 13, 2006, whichapplication is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a torque converter, in particular, a torqueconverter in which the output height of the output openings of thestator is higher than the input height of the input openings, producinga stator with a diffuser effect.

BACKGROUND OF THE INVENTION

Torque converters have been known since 1905 (DE 22 14 22 and DE 23 8804). The inventor, Föttinger, installed a pump and a turbine between twohalves of a shell which were joined together in a fluid-tight connectionafter assembly. In a further refinement of the invention, a stator isalso positioned. In the pump, the turbine and the stator there are vanesthat extend essentially radially. Filling the housing with afluid—preferably oil—brings about a transfer of force and torque fromthe pump to the turbine. The introduction of force into the torqueconverter in a motor vehicle occurs by having the housing of theconverter attached to the crankshaft of a combustion engine in arotationally fixed connection. The output takes place through theturbine, with the transmission input shaft of the subsequenttransmission being connected—directly or indirectly—to the hub of theturbine in a rotationally fixed connection.

Through the rotation of the housing—and hence of the pump—the oil isthrown outward by the effect of centrifugal force. The oil flows in anarc within the pump. In the radially outer area of the pump the oilstream is diverted in the axial direction and then flows into theturbine. The power that the oil must deliver slows the oil flow, so thatthe flow cross section in the turbine must expand increasingly in thedirection of flow. Since the oil must be directed again to the inflowarea of the pump, the outer wall of the turbine is curved toward theinflow area of the pump. Before the stream of oil coming from theturbine can again reach the inflow openings of the pump, the oil alsoflows through the stator. The stream of oil undergoes another change ofdirection in the stator, so that the flow against the pump vanes isoptimized maximally. The oil circulation can then begin again. As longas the circulation is maintained, and as long as the turbine rotates ata lower speed than the pump, torque can be transmitted. However, thecloser the turbine speed approaches the pump speed, the poorer theefficiency becomes.

The pump, the turbine and the stator together form the torus of a torqueconverter. The corresponding flow is then a toroidal flow. The conceptis derived from mathematics, since the rotating ring of oil at the sametime rotates around the rotational axis of the torque converter with itsaxis offset.

Since the invention of the torque converter, additional importantcomponents have been invented and added to the torque converter. Thebridging clutch, for example, represents an important improvement, sinceit can be actuated when efficiency is low. As a result, the powerflows—directly or indirectly—into the transmission shaft. Another knownimprovement provides for a torsion vibration damper—called a damper forshort—to be installed in the power path, so that inconsistencies in therotation of the crankshaft do not reach the transmission input shaft.

Also, many shapes for the torus have been invented in the last hundredyears, in order to improve the efficiency of the torque converter. Butin recent years a standard shape has evolved for the motor vehicle,which has now been adapted essentially only to the power requirement andto the possibilities for installation in the transmission.

BRIEF SUMMARY OF THE INVENTION

The object of the invention was therefore to search for possibilitieswhich improve the efficiency of the torus.

In a first embodiment of the invention, the stator is designed as adiffuser. This means that the cross section between the vanes of thestator expands from the inflow opening in the direction of the outflowopening. This causes the oil to be retarded in the stator. Since theexpansion cannot be extensive, because otherwise adjacent intermediatespaces (which are formed by the neighboring vanes) would have to besmaller, the expansion occurs in the radial direction. Computationalfluid dynamics (CFD) simulations have shown that the reduction of thestatic pressure in the pump results in more power from the torqueconverter. To achieve a reduction of the static pressure in the pump,the flow of oil in the pump must be accelerated from the inlet openingto the outlet opening, for example, making the input opening of the pumplarger than the output opening of the pump. In the state of the artthese two openings are the same. To prepare the flow of oil for the flowcross section of the pump before it enters the pump, the stator isdesigned as a diffuser.

In another embodiment of the invention, lengthening the outlet openingsof the turbine in the direction of the rotational axis of the torqueconverter while retaining the dimensions of the flow-through openings ofthe stator results in an improvement in the efficiency. This result wasunexpected. That is, according to the knowledge available in the art atthe time, there was no expectation that the improvement would occur.This improvement occurs even if the inflow openings of the pump arelengthened in the direction of the rotational axis of the torqueconverter. The two measures can also be combined. A simulation by meansof a special program found an efficiency improvement of 2 to 3 percentfor the two combined measures.

According to the state of the art, in the radially outer area of thetorus an outflow of the oil from the pump occurs that is substantiallyparallel to the axis of rotation of the torque converter. This isimportant so that an axial flow against the turbine can again occur.Because the shell in which the vanes of the turbine are located must beat a distance from the housing of the torque converter so that nocontact with the housing occurs, and because the outer flow surface inthe pump is formed by the housing itself, a ring-shaped step must bestamped into the housing at the transition from the pump to the turbine,so that the outer diameter of the pump is at the level of the outerdiameter of the turbine. However as a result, the outside diameter ofthe pump is always somewhat smaller than the adjacent diameter of theconverter. Since the fifth power of the diameter of the pump enters intothe formula for the efficiency and the output of a torque converter, itis desirable to maximize the diameter of the pump. According to anotherembodiment of the invention, the housing is formed without a step. Theshape of the housing will be described in further detail below inconnection with the description of the figures.

In another embodiment of the invention the torus shape varies from thestate of the art in such a manner that it undergoes shearing. Thisshearing is to be understood in that shearing is explained in the theoryof strength of materials, except that when shaping the torus it is notany shear stresses that are of significance, but merely the deformationitself. For further clarification we here refer to the description ofthe figures given below.

In a final embodiment of the invention, the torus is shaped so that thetoroidal flow is almost circular. This is achieved by making the insidediameter of the stator, i.e., the diameter of the stator hub, 0.5 to 0.7times the outside diameter of the pump.

BRIEF DESCRIPTION OF THE DRAWINGS

The nature and mode of operation of the present invention will now bemore fully described in the following detailed description of theinvention taken with the accompanying drawing figures, in which:

FIG. 1 is a partial cross-sectional view of a torus according to thestate of the art;

FIG. 2 is a partial cross-sectional view of a present invention toruswith outflow and inflow openings of the turbine or pump, lengthened inthe direction of the axis of rotation in comparison to FIG. 1;

FIG. 3 is a partial cross-sectional view of a torus according to thestate of the art;

FIG. 4 is a partial cross-sectional view of a present invention toruswith enlarged pump diameter in comparison to FIG. 3;

FIG. 5 is a partial cross-sectional view of a torus according to thestate of the art;

FIG. 6 is a partial cross-sectional view of a present invention torusthat is sheared on the turbine side in comparison to FIG. 5;

FIG. 7 is a partial cross-sectional view of a present invention torusthat is sheared on the pump side in comparison to FIG. 5;

FIG. 8 is a partial cross-sectional view of a torus according to thestate of the art;

FIG. 9 is a partial cross-sectional view of a present invention toruswith a diffuser stator in comparison to FIG. 8;

FIG. 10 is a partial cross-sectional view of a torus according to thestate of the art; and,

FIG. 11 is a partial, cross-sectional view of a present invention toruswith a nearly circular cross section.

DETAILED DESCRIPTION OF THE INVENTION

It should be explained in advance that reference labels which are notmentioned in the descriptive portion are to be taken from the list ofreference labels. Equivalent reference labels represent an equivalentelement. At the outset, it should be appreciated that like drawingnumbers on different drawing views identify identical, or functionallysimilar, structural elements of the invention. While the presentinvention is described with respect to what is presently considered tobe the preferred aspects, it is to be understood that the invention asclaimed is not limited to the disclosed aspects.

Furthermore, it is understood that this invention is not limited to theparticular methodology, materials and modifications described and assuch may, of course, vary. It is also understood that the terminologyused herein is for the purpose of describing particular aspects only,and is not intended to limit the scope of the present invention, whichis limited only by the appended claims.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skill inthe art to which this invention belongs. Although any methods, devicesor materials similar or equivalent to those described herein can be usedin the practice or testing of the invention, the preferred methods,devices, and materials are now described.

FIG. 2 is best viewed in light of FIG. 1, because the differences arewell illustrated by comparing FIG. 2 with FIG. 1, state of the art. Thecross-section through the torus shown in the figures consistsessentially of a pump 1, a turbine 2 and a stator 3. The outer contourof the pump 1 is formed by the housing 4. The torus rotates around anaxis of rotation 5, which is identical to the axis of rotation of thecrankshaft of a combustion engine. Through the cross-sectional depictionit is also possible to simultaneously see the outlines of the vanespositioned in pump 1, turbine 2 and stator 3. The vanes are curved inspace, but that cannot be recognized here due to the two-dimensionaldepiction.

The vanes of turbine 2 are arranged in a shell of the turbine, whichsimultaneously represents the outer contour of the turbine vanes. Thecurved inner contours of pump 1 and of turbine 2 are also coveredaccording to the state of the art by a shell, known as the inner ring.This configuration guides the toroidal oil flow between the outershells, the inner shells and the vanes. In FIG. 1, the inner diameters12, 13, 14 of turbine 2, stator 3 and pump 1 are all at the same level.

In FIG. 2, an embodiment according to the invention, the radially innerends of turbine outlet, or output, opening 8 and of pump inflow opening11 have been placed further inside from diameter 12. However, stator 3remains unchanged in its dimensions of the inlet and outlet openings 9,10. Although the inner diameters 12′, 13′ of turbine 2 and pump 1 aresmaller than that of stator 3, the result, according to a CFDsimulation, is nevertheless an improvement in efficiency.

In another embodiment of a torus according to FIG. 4, the outer diameter21 of pump 1, as shown in FIG. 3, has been enlarged to a greaterdiameter 21′. FIG. 3 shows the state of the art for comparison. In FIG.3, a step is located in the housing 4 of the converter in a transitionzone 20, and the outer diameter of turbine 2 corresponds to that of pump1. The enlarged pump outer diameter 21′ became possible because opening20 (for the outflow of the oil from pump 1 into turbine 2) is located atapproximately an 11 o'clock position in comparison to the 12 o'clockposition shown for opening 20 in FIG. 3. However, since the fifth powerof the pump diameter enters as a positive figure into the formula forthe efficiency and the output, the larger pump diameter 21′ represents aclear improvement in output and efficiency. In patent specification DE22 14 22 FIG. 6, in patent specification U.S. Pat. No. 1,199,360 FIG. 8,and on page 265 of the monograph “Vehicle Transmissions” from the year1994 by the authors Lechner and Naunheimer, respective toruses are shownwith respective separation lines between pump output opening 6 andturbine input opening 7 at about the 11 o'clock position. However, anoverall oval housing is indicated in these references, so that oilexiting from pump 1 necessarily must flow into the turbine, unlike theconfiguration of the present invention embodiment. The above referencesalso fail to specify the nature of the housing. For example, thesereferences do not teach an enlarged pump outer diameter 21′.

FIGS. 6 and 7 show another embodiment of the invention, with FIG. 5showing the state of the art. The housings are portrayed morerealistically here than in the earlier figures, but the indicated axialconnecting technology in the radially outer area is atypical for seriesproducts. The illustrated connecting technology is used in theexperimental realm, to enable installed parts of the converter to beexchanged faster and more easily. In the case of series products, theleft and right housing shells are welded together at the circumference.To clarify the presentation, the converter bridging clutch and torsionvibration damper components are intentionally not shown in thesefigures.

According to one aspect of the invention, the torus is sheared in eachcase in FIGS. 6 and 7. In FIG. 6 there is shearing in the direction ofturbine 6. In FIG. 7 the torus is sheared in the direction of the pump.To prevent misunderstandings, it should be emphasized that the examplesin FIGS. 6 and 7 do not show a tilted torus. If the torus were tiltedinstead of sheared, then, for example, the lowest point of FIG. 5 (stateof the art) between turbine output opening 8 and stator input opening 9in FIG. 6 would be lower than the intersection of the verticaldashed-dotted line and the center line C. In FIG. 7 the vertical line ispositioned in the center of the inner stator outlet diameter 12. This isillustrated by the intervals a, b, which are both the same size. If oneimagines an infinite number of assumed axial sections through the torus,and if they are shifted with an increasing effective radius 15,increasing, axially in the direction of the pump, a sheared torusresults. At the level of the pump outer diameter 21, the value Srepresents the total magnitude of the shearing.

The shearing has the advantage that in FIG. 6 there is more space in theradially inner area for installed parts—for example for a torsionvibration damper—and at the same time the total length of the converterbecomes shorter compared to the existing art. The maximum availableaxial construction space is increasingly a problem for the designers.With the shearing according to FIG. 7, space has been created in theradially outer area. This construction space can be used specificallyfor a damper, since a damper effects a larger spring deflection withincreasing effective diameter.

From the state of the art (DE 10081340 T 1, FIG. 14 and U.S. Pat. No.4,129,000, FIG. 1), torus forms are known that look similar to thepresent invention, but either no parallelism of the pump output opening6 to the turbine input opening 7 is revealed there, or the parallelismdoes in fact exist but this transition point is of radial form and notsheared.

If pump output opening 6 and turbine input opening 7 are not parallel,efficiency is lost. The decisive advantage of this inventive embodimentis that the torus form can be produced through axial shaping processes.This is especially advantageous in the case of the stator 3, whichaccording to the state of the art is produced by aluminum die casting,because costly slide tools are made superfluous by the axial shapingemployed there.

FIG. 9 shows an additional embodiment, with FIG. 8 showing the state ofthe art. In this embodiment of the invention, stator 3 is provided witha diffuser effect; i.e., the oil is retarded as it flows through. Thisis achieved by having the stator output openings 10 designed longer thanthe stator input openings 9. Since an expansion of the cross sectionbetween the vanes is not permitted in the circumferential direction, andsince then the cross sections between the adjacent vanes would bereduced, the cross section is expanded in the radial direction. For thatreason the input height 17 is smaller than the output height 16. Thisdesign has the advantage that when the stator 3 is produced by means ofdie casting it is possible to use axial deformation. The expansion canbe accomplished either by having only the outer ring-shaped boundarysurface 19 open radially outwardly, by having only the inner radialboundary surface 18 open radially inwardly (not shown), or by combiningthe preceding radial openings (not shown). As already explained earlier,the design of stator 3 as a diffuser also has hydrokinetic benefits. Inanother embodiment of the diffuser, the outer ring—which is provided onthe inside with the outer ring-shaped boundary surface 19—can bedesigned as a separate ring. This ring can then be pressed onto theouter diameter of the stator vanes by pressing. In additionalembodiments this ring can also be secured on the stator vanes by meansof a step, a groove, or by staking.

From the state of the art, for example in patent specification U.S. Pat.No. 2,737,827, a converter is known that also has a diffuser-typestator. However, the converter depicted there is a converter that hasmore than three torus sections. In the claimed invention on the otherhand, there are a maximum of only the three torus sections, namely pump,turbine and stator. In addition, in the state of the art the statorcannot be produced by means of an axial deformation, because thisresults in an undercut due to the curvature in the radially outer areaof the inflow end. It would not be possible then to pull a core out tothe right.

FIG. 11 shows an embodiment of the invention, with FIG. 10 showing thestate of the art for direct comparison. The shaded narrow areas in pump1, turbine 2 and stator 3 come about because the vanes are also drawn inhere, and they are also cut in part by the sectional plane. Thehorizontal lines are intended for better comparison of the constructionsizes. It is conspicuous that stator 3 in FIG. 11 has been pushed intothe torus to a certain extent. The formerly oval torus of FIG. 10 hasbecome an almost circular torus in FIG. 11. The inside stator diameter14 is shifted radially to the stator diameter 14′. In the same way, theouter stator diameter 22 is shifted radially outward to the outer statordiameter 22′. The inner stator passage diameter 14′ is preferably 0.5 to0.7 times the outer diameter 21 of the pump.

Converter output data are typically depicted in a diagram of “MP 2000(Nm)” over “speed ratio.” Here “MP 2000” is the input torque of the pumpin Newton meters at 2000 revolutions per minute. The “speed ratio” isthe ratio of the rotational speed of the turbine to the rotational speedof the pump. Since the rotational speed of the turbine without aconverter bridging clutch is always lower than the rotational speed ofthe pump, with a disengaged converter bridging clutch this value is alsoalways less than 1. In such a diagram (not shown) for the presentinvention of FIG. 11, the pump torques for small speed ratios (<0.5) arelower than the values for the existing art. This is especiallybeneficial when a combustion engine is first to be disengaged in itslower speed range, i.e., is not yet to be loaded to the full extent bydriving power. This is especially important for diesel engines.

The present invention performs differently however at an upper speedratio (>0.5). Here the pump torques are greater than those of the stateof the art. This is also advantageous if the efficiency worsens as thespeed ratio approaches 1 (or 0.8, the possible clutch point), but theturbine power can nevertheless be increased in this speed range by theinvention. The turbine power is the power that is ultimately forwardedto the transmission.

Thus, it is seen that the objects of the present invention areefficiently obtained, although modifications and changes to theinvention should be readily apparent to those having ordinary skill inthe art, which modifications are intended to be within the spirit andscope of the invention as claimed. It also is understood that theforegoing description is illustrative of the present invention andshould not be considered as limiting. Therefore, other embodiments ofthe present invention are possible without departing from the spirit andscope of the present invention.

REFERENCE NUMBERS

-   1 pump-   2 turbine-   3 stator-   4 housing-   5 axis of rotation-   6 pump output opening-   7 turbine input opening-   8 turbine output opening-   9 stator input opening-   10 stator output opening-   11 pump input opening-   12 inside turbine output diameter-   12′ reduced inside turbine output diameter-   13 inside pump input diameter-   13′ reduced inside pump input diameter-   14 inside stator passage diameter-   15 effective radius-   16 output height on the output side of the stator-   17 input height on the input side of the stator-   18 inner ring-shaped boundary surface-   19 outer ring-shaped boundary surface-   20 transition area-   21 pump outside diameter-   21′ enlarged pump outside diameter-   22 outside stator passage diameter-   22′ outside stator passage diameter-   W axial width of the torus-   S shearing-   C center line-   a separation-   b separation

1. A torque converter for a motor vehicle, comprising a housing and apump located therein, a turbine, a stator, and a bridging clutch,wherein the pump, the turbine and the stator together form a torus,where the stator has respective pluralities of inlet openings and outletopenings, wherein an output height at the plurality of output openingsof the stator is greater than an input height at the plurality of inputopenings of the stator, wherein an outer ring-shaped boundary surfacefor the stator is disposed, with respect to an axis of rotation for thetorque converter, radially outside of an inner ring-shaped boundarysurface for the stator, wherein the outer ring-shaped boundary surfacesforms a portion of the input and output openings of the stator, andwherein a first radial distance, from the axis of rotation to the outerring-shaped boundary surface at the input openings is less than a secondradial distance from the axis of rotation to the outer ring-shapedboundary surface at the output openings.
 2. The torque converter ofclaim 1, wherein a diameter of an inner, ring-shaped boundary surface atthe output openings of the stator is smaller than a diameter of theinner ring-shaped boundary surface at the plurality of input openings ofthe stator.
 3. The torque converter of claim 1, wherein the statorcomprises a plurality of vanes, and wherein an outer ring-shapedboundary surface is designed as a separate ring that can be slid onto anouter diameter of the plurality of vanes.
 4. The torque converter ofclaim 3, wherein the separate ring is fixed on the plurality of vanes byone of a step, a groove, and staking.
 5. The torque converter of claim1, wherein the pump comprises a plurality of output openings, theturbine comprises a plurality of input openings, and the plurality ofoutput openings of the pump form a cone-shaped figure, the figuredesigned so that an outer rim of the pump extends farther toward theturbine than an inner diameter of the pump, and so that the plurality ofinput openings of the turbine are essentially parallel to the pluralityof output openings of the pump, where a diameter for a portion of thehousing radially aligned with a transition area from the pump to theturbine is uniform.
 6. The torque converter of claim 1, wherein an innerstator passage diameter is 0.5 to 0.7 times an outer diameter of thepump.
 7. The torque converter of claim 1, wherein at least one of aninner turbine output diameter and an inner pump input diameter issmaller than an inner stator passage diameter.
 8. The torque converterof claim 1, wherein an inner turbine output diameter and an inner pumpinput diameter are smaller than an inner stator passage diameter.
 9. Thetorque converter of claim 1, wherein a shape of the torus is sheared sothat so that imagined axial sections through the torus shape, startingfrom an inner stator passage diameter, are shifted increasingly axiallyin one direction as an effective radius increases.
 10. The torqueconverter of claim 9, wherein the shearing is linear so that over therunning variable of an effective radius a quotient of the axial shift tothe difference in effective radius is constant.
 11. The torque converterof claim 9, wherein the torus shape is sheared in the direction of theturbine.
 12. The torque converter of claim 9, wherein the torus shape issheared in the direction of the pump.
 13. The torque converter of claim1, further comprising at least one torsional vibration damper.
 14. Atorque converter for a motor vehicle, comprising a housing and a pumplocated therein, a turbine, a stator, and a bridging clutch, wherein thepump, the turbine and the stator together form a torus, where the statorhas respective pluralities of inlet openings and outlet openings andwherein a diameter of an outer, ring-shaped boundary surface of thestator at the plurality of output openings of the stator is larger thana diameter of the outer ring-shaped boundary surface at the plurality ofinput openings of the stator.
 15. A torque converter for a motorvehicle, comprising a housing and a pump located therein, a turbine, astator, and a bridging clutch, wherein the pump, the turbine and thestator together form a torus, where the stator has respectivepluralities of inlet openings and outlet openings and wherein a diameterof an outer, ring-shaped boundary surface of the stator increasessubstantially continuously from the plurality of input openings of thestator to the plurality of output openings of the stator.